[Vwdiesel] Turbo vs. Non-turbo [was My TURBO test (more scientific)]

[LBaird119 at aol.com]

  Wow did I miss a thread or what?!?  ;-D
  I'll throw in my £2.00 worth.  Most of it is personal opinion formed from
various readings, personal observations and educated guesses that I
generally cannot prove but still have arrived at also usually inexplicably.
  Gas EGT:  Biggest reason the gas EGT is higher (IMO) is because so
much of the engine's combustion takes place in the exhaust manifold.
Remember the smog pump?
  The comment about diesels needing more air to properly burn the fuel?
One problem with this.  Typically a gas engine not only has virtually no
O2 in the exhaust, there is unburned HC to a relatively high percentage.
Diesels (it's been said) ALWAYS have O2 left after combustion.  I guess
you could call that efficient or incomplete depending on how you want to
look at it without definitive study.  Even though we know warmer gas makes
for better combustion, most people strive for the coldest intake they can
manage for more density over efficient combustion, when peaking performance.
Diesels don't have to fret about puddling, dropping out of suspension, etc.
  Turbo or not here I come!
  Early 80's article I have resulted in an increase in mpg as well as power
with a BAE turbo on a 1.5 Rabbit.  My Dasher had a minor mpg increase
with addition of the same.  I gained almost as much again when I turned
up the fuel delivery. I attributed it to spending less time at full
"throttle"
(yeah, our little lever isn't technically a throttle) when accelerating.
Even
though you are capable of using more fuel, you use it for less time.
Another example:  Dad's pickup made the worst mileage it's ever done.
It made 30 or 33 (don't remember for sure at the moment, I think it was
33).  The boost enrichment hose had come off.  Part of it could be
attributed to the lost air but it is a small hose.  After fixing that and the
valve adjustment, I made 40mpg and with a heavier load, on about the
same trip.  Unless you USE that extra fuel you shouldn't get worse mileage
with a TD.  My uncle got considerable worse mileage in his 6.9 Ford.  He
tends to romp the throttle every time he wants to speed up regardless of
it being 1mph or 50 that he wants to gain.
  Full boost:
  Depends on what you call that.  It can be both ways.  Sure James can
hit full boost probably anywhere above 1300 to 1500 when he stomps it,
if you call full boost 10psi.  For most arguments this is the case.  I
haven't
had the time to spend on getting to that point without much more smoke
than I'll tolerate.  I tend to see more up to about 7 to 9 psi on demand
and only seeing 10+ on a good hill after a short time.  For most of us this
is probably closer to reality.  I see about 7psi at 65 to 70mph on level
ground.  The old rabbit article and my Dasher observations were in the
55mph days.  Great for 1:1 comparisons but lousy for getting from
point A to B!  Now you go through many different limits and enforcement
isn't as stringent so there are a lot more speed variables.  With our A1
bodies especially, the faster we go, the wind drag seems to go up
proportionally.
  Torque vs HP:
  Put very simply, torque is, as said a measure of the amount of "push"
the pistons exert at a given moment.  HP is a combination of torque
plus rotating mass.  Raise the rpm, raise the hp on the same engine,
with no changes.  Put on a heavier flywheel and you stand a good
chance of raising the hp rating as well.  ;-)
  Part of why a gas turbo doesn't last as long is that last 30% IMO.
Driver error.  Gas owners aren't as smart or good looking as the diesel
crowd.  Therefore they don't know it and don't have the charisma to be
blindly approached and offered advice on cool down procedure as part
of a "pick up" line.  ;D  They don't run as good of oil as we do, are more
likely to ride it hard and put it away hot and not maintain (necessarily)
as well.  My sister's Capri Turbo got 70K before it destructed.  First time
most facilities had seen such a thing.  It still had the ORIGINAL air filter
in it!  STUPID!
  Something for Nothing:
  On a diesel, sort of.  I believe there's a bit of overlap so the boost will
help evacuate the cylinder.  This certainly happens on a 2 stroke diesel.
Back pressure prevents full cylinder evacuation however there is very little
combustion chamber on a diesel. :)  The boost helps drastically to fill the
cylinder what with no throttle plate (except Mercedes anyway).  This likely
helps radically in the turbo gas to TD comparison.  You don't want much
overlap in a gas as you blow your fuel out the exhaust unlike a diesel.  I
see this giving you very close to benefit without cost (not monetarily) with
a diesel.  Your foot can negate this if the local gendarme allows it.
  Sizing:
  Simply put, smaller turbo = faster spool up.  Bigger turbo = slower spool
up.
Smaller turbo can physically become a restriction at higher rpm.  Bigger
turbo can produce more maximum hp.  Turbos used to mostly size for
the small end of the bigger turbo such that it can only produce maximum
desired boost at maximum rpm under maximum load.  No wastegate so
less parts = better was the idea.  I never bought into that even though I
own one such setup.  Most systems now are more on the higher end
of the smaller turbo for a balance between the two.  You're not likely to
pass the surge line on our turbos because of the integral wastegate.
That's what they're for.  I'd like to see a turbo with a little smaller A/R
on the exhaust side or some ceramic bearings or such to make the
intake side "faster."  A larger intake A/R would do that if you can do
it without more mass or with less drag.
  I've given a lot of though of putting a Subaru IHI turbo on the Rabbit
instead of the factory one when I add it.  Jake said he talked to
someone that did just that and was running 30 psi on a Vanagon.  :)
Dad's newest tractor has a 2 or 2.2l TD.  It has a noticeably smaller
turbo that you can hear winding up at off-idle!  Of course maximum
rpm is about half of a VW.  Still, the pull it has is overwhelming. :)
   Too many back space typos and foggy brain to continue.
     Loren